A Brayton cycle typically describes the process for gas turbine engine. Ambient air is drawn into the compressor, where it is pressurized in a theoretically isentropic process. The compressed air then runs through a combustion chamber, where fuel is burned, heating that air usually in a constant-pressure process, since the chamber is open to flow in and out. The heated, pressurized air and combustion products then give up their energy, expanding through a turbine another theoretically isentropic process. Some of the work extracted by the turbine is typically used to drive the compressor.
Many variations of the Brayton cycle for turbines are in use and have been described in the prior art. Typically, these embodiments work best with a constant temperature maintained in the motive fluid at the turbine inlet. This is the principle reason that most applications of Brayton cycle engines involve the production of electricity and are not recommended for motive power for a vehicle. One of the methods of the present invention is controlling the power output of the heat engine and thus enhancing a vehicle transportation application, by regulating the temperature of the motive fluid.
None of the prior art describes the indirect addition of heat to compressed air as a motive fluid in an open Brayton cycle that does not employ combustion products as part of the motive fluid. Further, none discloses the addition of heat to the compressed motive fluid solely by operation of a closed-cycle heat pump where the evaporation side of the heat pump is heated by a combustion source. None, thus enables flexfuel capability, that is, flexibility in fuel utilization through an isolated combustion source; high efficiency due to high heat transference to the motive fluid; simplicity due to the use of atmospheric air as the motive fluid, and prolonged turbine life by exposing the turbine blades only to a clean air motive fluid, rather than depleted air and combustion products.
Typical of the prior art, internal combustion efficiencies are not being directly addressed, except by making incremental improvements to engine and vehicle designs. No current internal combustion engine research is devoted to a radical departure from the basic operation of such an engine, as is the case with the present invention.